The purposes of this study are: 1) to compare the frequency and distribution of five phenotypes in black hypertensives versus black normotensive controls and assess the correlation of each phenotype to the other and to the sodium sensitivity of the blood pressure; 2) to determine if particular phenotypes show familial aggregation in hypertension sibling pairs; 3) to search for linkage of the renin gene locus to genes predisposing to hypertension in black hypertensive sibling pairs.